There are two points that I wanna bring up that I think both the devs and we as players need to be aware of and consider carefully:
First off, DCUO DOES in fact root you during attack animations. Yes, I know you don't believe me, but let me explain
And if you want to see for yourself, you can always download the game for free.
Let me explain how it works in DCUO as best as I can. As most should be aware, there are two methods in which players can attack in DCUO; weapons and powers. In regards to weapons, I would say 99% of all weapon actions will disable WASD control until your character completes their animation. The only two exceptions I can think of are tap right clicks and the spinny AOE attack of the Two Handed weapon tree. There may be a few more exceptions I don't know about, but I doubt they're in any significant number. For the vast majority of weapon actions, it behaves like this: tap left clicks are light melee attacks that move your character forward one step towards your target unless you're colliding with another hitbox; hold left clicks are gap closers that will lunge you forward and put you as close to your target's hitbox as it can; hold right clicks are heavy ranged attacks that root you in place completely. In all cases, WASD is disabled and the player is locked into the animation until it completes.
In regards to powers, I would say that it is at least a 60-40 split in favor of rooting. Most power abilities will root you completely; some are gap closers/extenders that will disable WASD control but move you backwards or forwards automatically; some allow you WASD control at a walking pace during the animation; very few allow you WASD control at a jogging pace during the animation. That fact that "animation clipping" exists in DCUO is proof of this, as it is a technique (or controversially, an exploit), that allows players to circumvent the animation lock of certain powers, so they can either continue attacking earlier for more DPS, or move away if they're about to get squished by a boss.
I feel like this is important for people to understand because there is obvious irony in that DCUO has been practically universally regarded as "more actiony" than CO in terms of combat, when in fact it restricts movement much more. As far as I remember, the only time WASD is disabled in CO is during gap closers/extenders. Every Maintain or Charge can be finished early at the discretion of the player. I know that at least some Charges (Haymaker) allow you to cast while moving around, and yes you can in fact deliver a rapid flurry of kicks to your target while sliding around on one foot (Thundering Kicks). It's arguable that CO allows the player much more use and speed out of their travel power during combat as well.
The conclusion I draw, and that I think everyone should consider, is that movement is not all that important in regards to the "action" of the game, rather that PACING and ANIMATIONS are the things that are most influential in making people go "ooh" and "ahh". CoX animations took too long and looked too bland, that's why some people found it boring. DCUO animations rarely last longer than 1 second, and have your character spinning around and doing somersaults. They both root you in place, however DCUO succeeds because it has better animations and faster pacing so you largely don't even notice that you've been locked in place. CO's pacing consists of charging haymaker or maintaining two gun mojo over and over and over again until the boss dies, that's why some people find it boring. DCUO is often more akin to a traditional MMO that features DPS rotations and buff management and that keeps players engaged. The fact that CO allows players more freedom to move around is meaningless since its pacing is too monotonous.
Now, my second point is shorter and more aimed towards the developers' considerations. I know that most of my first point looks like an endorsement of rooting and animation locks, but I assure you it's not the case. I only made that point as food for thought, since combat and fun ARE complex issues. However, personally, I am still concerned when I hear about a combat system that will feature rooting.
The reason I'm concerned is that the vast majority of MMOs out there do not restrict movement in any real way. Notice how in WoW, or SWTOR, or in most any MMO that would come to mind, you see players freely circle-strafing around each other in PVP while they're attacking, and there is no detriment to the game's balance there - in fact it can be a benefit. Some of my fondest experiences in SWTOR were force-pushing people off cliffs or dodge-rolling through a fire trap right before it activates and leaving my pursuers stuck on the other side.
It seems like successful MMO combat that feature animation rooting are very much the exceptions. I can only mention DCUO as one, and I THINK Tera is another (just based off of gameplay vids). Statistically, the odds are against animation rooting, so I hope the devs are very careful and deliberate if they want to go down this route. I don't think it's impossible for combat to be fun without free movement - as I said, I think that movement is secondary compared to pacing and animations - but I just want to urge the devs to consider and learn from both the successes and failures of the MMOs that have come before them.